High-redshift Fermi blazars observed by GROND and Swift

G. Ghisellini, M. Nardini, J. Tagliaferri Greiner, P. Schady, A. Rau, L. Foschini, F. Tavecchio, G. Ghirlanda, T. Sbarrato

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13 Citations (SciVal)


We observed five γ-ray-loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) on-board the Swift satellite, and the Gamma-Ray burst Optical Near-Infrared Detector (GROND) instrument. These observations were quasi-simultaneous, usually within a few hours. For four of these blazars, the near-IR to UV data show the presence of an accretion disc, and we could reliably estimate its accretion rate and black hole mass. One of them, PKS 1348+007, was found in an extraordinarily high IR–optical state, almost two orders of magnitude brighter than at the epoch of the Sloan Digital Sky Survey observations. For all the five quasars, the physical parameters of the jet-emitting zone, derived by applying a one-zone emission model, are similar to that found for the bulk of other γ-ray-loud quasars. With our observations, we have X-ray data for the full sample of blazars at z > 2 present in the Fermi 2-year (2LAC) catalogue. This allows us to have a rather complete view of the spectral energy distribution of all high-redshift Fermi blazars, and to draw some conclusions about their properties, and especially about the relation between the accretion rate and the jet power.
Original languageEnglish
Pages (from-to)1449-1459
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date26 Oct 2012
Publication statusPublished - 11 Jan 2013


  • galaxies: jets
  • galaxies: active
  • radiation mechanisms: non-thermal


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